The invention relates to electronic labels for systems for displaying prices, in particular in stores of the hypermarket type.
Electronic labels such as those described in document EP 0 447 278 include means for receiving information coming from a central station. Those receiver means include a receive antenna electromagnetically coupled with a current loop constituting the transmit antenna of the central station.
However, although the central station is capable of sending arbitrary information to a given label, it is not capable of receiving information from said label unless the label is itself fitted with means for transmitting information to the central station. Such transmitter means include a transmit antenna electromagnetically coupled with a receive antenna of the central station.
For example, the use of a traditional transmit antenna would require the antenna to be constituted by a wire having a length of about 17 centimeters (cm), which is an antenna length suitable for use with frequencies of about 433 megahertz (MHz), and for the antenna to project outwards from the label perpendicularly to a main plane of the label housing, in order to transmit under good conditions. That would lead to the label occupying an amount of space that is not compatible with the label being used on the shelves of a store of the supermarket or hypermarket type, for example.
In addition, it would be very expensive for the label to use a transmit antenna comprising a ferrite rod, even though such an antenna would be smaller in size, and thus more compatible with the intended use. In order to operate, such an antenna needs to be very accurately adjusted, thereby considerably increasing the cost price of the label.